1. Field of the Invention
The present invention relates to a hydraulic circuit having a direction changing valve that changes supply and discharge directions of hydraulic oil between a pump, a tank, and an actuator, a pilot check valve, and an overload relief valve, and its valve gear.
2. Description of the Related Art
Conventionally, a hydraulic circuit having a direction changing valve for changing supply and discharge directions of hydraulic oil between a pump, a tank, and an actuator, a pilot check valve arranged between the direction changing valve and the actuator, and an overload relief valve for discharging the excess hydraulic oil; and its valve gear have been known (refer to Patent document 1). In the hydraulic circuit and the valve gear described in this Patent document 1, the pilot check valve (a lock valve mechanism v in Patent document 1) and the overload relief valve (a relief valve 40 in Patent document 1) are communicated with the pump and the tank through the paths that are separately provided.
Patent document 1: JP-A-6-50302
However, in the hydraulic circuit and the valve gear described in Patent document 1, as described above, it is necessary that the pilot check valve and the overload relief valve are communicated with the pump and the tank through the separate paths. Therefore, this involves a problem such that the circuit structure is complicated as the hydraulic circuit and the structure of the path formed in the valve gear is complicated. As a result, the valve gear itself becomes enlarged.